Commuter is a person who travels everyday to work. It happens in big cities, because people live outside the city, and live in the surroundings, because flats and food is cheaper.
Some people are lucky enough to work at home or live very close to where they work. Others are commuters: commuters need to travel to work. Being a commuter isn't easy, because it might take anywhere from 20 minutes to two hours to get from home to work and then back again.
In Spain, we can find commuters in Madrid and Barcelona. You have to take the tube, the train, the bus, etc, to go from one place to another. I have an aunt in Madrid, and some cousins, and they travel everyday, for one hour or two.
I don't like spending a long time in transports, so I prefer to live in small cities or villages where everything is near.